Tuesday May 7th, 2013

Weight Management for captive companion parrots is a necessity but does not get the attention it deserves. Like wing clipping, free-feeding is still the status quo. But just like wing clipping, free-feeding is neither natural nor healthy for parrots. In this and the next few articles, I am going to share with you some of my success with using food management and why you should too. The intricate details of actually applying it, however, I'm going to suggest you buy my book which will be out by the end of the month. Stay tuned.

Some people mistakenly think I starve my parrots to get them to perform. Neither of these things are true. First of all, they are not starved and I will get into this in great depth in this article. Second of all, I don't weight manage my parrots for doing tricks! I will go into great length about motivation (and how food management applies to it) in the next article. But the important point that I want you to leave with is that number one reason I weight manage my parrots is for their health!

I would weight manage Kili & Truman entirely regardless of tricks, shows, and training. There are periods of time (sometimes months) when I'm too busy or too lazy to train them as regularly as I usually do. Yet I still weight manage them during these periods because I am convinced that this is healthier for them. Their health and well being is of paramount importance to me and I'd give up the tricks if they were in any way conflicting. But the good news is that they're not. The byproduct of the weight management that I do for health is food motivation for training (which will be covered next time).

There is nothing natural about free-feeding your parrot by leaving food in its bowl all day long. Parrots in the wild do not spend all day eating. They neither need to, want to, nor are able to. Although they "could" decide to try and eat at times they shouldn't, they won't. And that is because the outcome would likely be a bad one. First a simple example that I doubt anyone would argue against. Night. The parrot is not going to get off its roost at night to go searching for food. Even though it has the freedom to go eat at night, it doesn't. It would probably crash into a tree (like George of the Jungle) trying to fly at night! Thus it is silly for parrot owners to be leaving food in the cage over night. The parrot won't be eating it but it will attract nocturnal pests such as bugs and rodents. So don't leave food in the cage at night.

Now let's look at daytime feeding. In the wild, you generally won't see parrots (and in fact most birds) eating in the daytime. In fact you won't see them at all because they are probably in some tree napping. During all my travels in Africa, the only time I have seen African parrots eating (or out and about) was in the morning and evening. In the mid-day time, it is too hot and too dangerous for a parrot to be out getting lunch. Birds of prey take advantage of daytime air currents fly around and catch the birds that couldn't wait till evening to eat. The heat is also a problem because it becomes more difficult for parrots to fly in extreme heat. Since most parrots are equatorial, this plays a significant role as well.

Thus in the wild parrots don't really have access to food all day long. They only eat in the morning and evening. Since this is the schedule that the environment demands, parrots are evolved to best function with this kind of feeding. Their metabolism, crop, and other aspects of their digestive system optimize them to take in food and use the energy accordingly.

The other aspect of food management that naturally happens in the wild is weight management. In fact this is true of all animals. Simply put, there's not enough food for everyone. So many animals just don't make it. The ones that do, are getting by on the bare minimum. But that's ok because millions of years of avian evolution has lead to the highly efficient bodies that these parrots now posses. They are like that car that gets the best gas mileage. Even on the last gallon of gas, they'll go very far.

In the wild, food portions are regulated by the environment as well as the competition. Sometimes there is more plant matter (food) and other times there is less. When there is less, the strongest parrots make it and the weaker ones die. When there is a greater food abundance, the strong ones still eat but the weaker ones get to live too. For this reason, the amount the birds get to consume is rarely more than the minimum. Occasionally there are opportunities to really pig out (for example a fruit tree just blossomed). Parrots take that opportunity to stuff themselves to the limit because future feedings are never certain. They may go days without food afterward.

Parrots have no natural shut off mechanism when to stop eating besides being stuffed to the max. In the short term this is ok but in the long term it leads to obesity. Since there is so little food and so much competition in the wild, the bird will quickly return to equilibrium. In the unnatural household environment with a constant supply of food, the parrot will act on its instinct to stuff itself now. But it will continue to do so daily because that natural food limit is never restored that will take its weight back down. In the wild parrots don't need to "know" when to stop eating to be healthy. The resource limits and competition naturally dictate this and millions of years of evolution have optimized the parrot's body to work with that natural limit. All of the parrots that required a differing amount of food than the environment would offer died before they could reproduce. This not only includes the ones that couldn't get by on too little food. This also includes the ones that may have eaten too much to the point where obesity degraded their bodies. But since food tends to be on the low side rather than high side, the natural instinct for the bird is to top off now just in case.

Understanding the natural constraints that work in the wild help us realize that unlimited food availability is unnatural and unhealthy. The parrot is driven to eat as much as it can to protect against later deprivation but since it never comes, the parrot ends up overweight. But this problem of becoming overweight goes beyond just the amount of food eaten. It also has to do with many other unnatural factors. The parrots are fed too much food, with too many calories, that is too easy to get, with too little exercise! All aspects of household pet life for the parrot drive it toward obesity.

Parrots have strong immune systems and tend to stay healthy. However, they do not have good defenses against obesity. The reason is simple, you don't see obese parrots in the wild so they don't need to have evolved protection against obesity problems. They sooner have natural ways of surviving and dealing with excess hunger than excess weight.

When you come to think of it, the same hold true for people. Even though we "could" eat at any part of the day, we don't. Or at least we shouldn't. Humans tend to eat at several scheduled meals a day as well. We don't go around eating all day long and neither should our parrots. And when people do eat a little all the time, they tend to get overweight and not feel good. Just think about sitting around with friends with some tapas or snack foods around. After a few hours, you are beyond stuffed and can't believe how much you ate a little at a time. Likewise for the parrot that is presented with food all day long, even if it doesn't really need or want it, it picks at it just because it's there. The bird ends up eating food that it could really do without. Eating out of boredom is unnecessary as well as unhealthy. Human children tend to stay pretty fit while they are young because they don't have non-stop access to food and only eat when their parents feed them. But as we get older and our access restrictions are lifted, it is harder to keep the weight off. Instead of thinking of food/weight management as deprivation, think of scheduled/portioned meals as healthy feeding for a child.

Whether seeds, pellets, fruit, or other household foods, the things we feed our parrot are generally far more packed with calories per mouthful than what they would eat in the wild. Fact is most of these foods are engineered for maximum yield for human consumption (or at least chosen for it). Since there are more calories in the food by volume, even if the parrot tries to eat the amount that feels right to it (without intentionally putting on fat for a rainy day), it will get more calories than naturally. Next, the parrot isn't spending any energy to actually eat the food. The household parrot simply eats the food out of a bowl instead of flying for miles, climbing, and foraging for it. Lastly, since the parrot is confined, it simply cannot get as much exercise as it would in the wild.

Most parrots spend a lot of time in a cage. This is time they are not flying and barely climbing. Most parrots are clipped and can't even get any exercise when they are out of the cage. But even the ones that are flighted can only fly short distances in the confines of our home for the limited time that we let them. Even well exercised parrots like Kili & Truman get far less flight and exercise than their wild counterparts. They only spend about an hour a day flying at home during training. Even when I take them to the park or gym to fly, that's only a few days a week. Wild parrots don't get a day off. They are flying and working hard every single day. So no matter how many calories they consume in their limited food, they end up spending it all for feeding again and living.

Since it is outside of our capability to give our parrots the same amount of exercise that would be mandated by the excessive food abundance they consume, training and weight management are the things we must resort to.

The overweight parrot is also the parrot that is hardest to give sufficient exercise. Even flighted, the overweight parrot is not motivated to fly for food and it is hard for it to fly because it is heavy. For airplanes, you need to quadruple the power when you double the weight. So for a parrot that is 10-30% overweight, flying requires 40-120% as much effort. The numbers may not be exact but it should illustrate why excess weight can adversely affect a parrot's weight both directly and indirectly. Directly by leading to obesity related problems. Indirectly by discouraging it to fly and thereby preventing it from getting sufficient exercise.

While motivation to fly for food is stronger when the parrot is more hungry, the direct affect of the weight plays as much if not a greater role! Over the years I have watched how my parrots fly at different weights and have definitely seen a huge difference. Even when the motivation exists for the parrot to fly while at a heavy weight (example is the parrot is overweight but then misses a meal), you can tell that the parrot is struggling to stay airborne. The parrot has to fly faster, you hear more flapping noise, and the parrot tire out much quicker. This is as strong a deterrent from flying as there can be. On the flipside, when my parrots are on the lighter side, I have discovered that it takes far less food related motivation for them to fly. Even after a meal when they are no longer hungry, they are more likely to willingly fly. The lighter weight parrot will fly more because it is easier for it to fly. Less motivation is required to get it to fly because it is easier and the rewards are sooner justified.

This leads to discovering the cyclical nature of the polar opposites of a parrot's weight. Either the bird is going to be light, fit, and healthy or heavy, obese, and suffer health problems. There is basically no middle ground. The heavy parrot will eat a lot, exercise little, fly little, and thus stay heavy. The light weight parrot will have a lot of food driven motivation, fly eagerly, get more exercise, and become stronger. As the light parrot becomes stronger (from flying a lot), it will be able to fly with even greater ease and thus be able to get even more exercise flying for even less food reward.

Another reason it is unhealthy for parrots to be on the heavy side has to do with hormones and reproduction. An overweight parrot is more likely to become hormonal and develop behavioral problems related to that. Those parrots get less out of cage time and attention because people have trouble dealing with them so they tend to remain caged more with little left to do than eat. The heavy parrot is more likely to lay infertile eggs and become egg bound. The lean parrot that has just enough to sustain itself but not another, is less likely to become hormonal or lay eggs. The lean parrot is more focused on feeding itself and its own survival to be in the reproductive state that can cause those other behavioral and health problems.

Thus the healthier approach to keeping companion parrots is to properly manage their food intake to keep them at a healthy weight. Usually, that healthy weight is well below the weight the parrot is on free-feed. In fact free-feed weight shouldn't even be used as a standard or be called normal weight. Free-feed weight is unnatural and is actually overweight for what the parrot would naturally be. So when a reduction of weight from free-feed weight is discussed, it's usually to get the parrot to stop being overweight rather than some kind of deprivation.

Parrot's food intake should be managed such that they attain and maintain the optimal healthy weight as can be inferred from body condition by an Avian Veterinarian. I am not suggesting that the target weight should be determined by behavior, mathematics, guesswork, or chance.

Kili & Truman recently paid the avian vet a visit for a check up. Partly because it is about time for an annual check up, partly because I wanted an outside opinion about their weight and body condition, and most importantly because I'm having a baby. I want to ensure that my existing birds are in top health before I add another. You can watch the videos of two separate avian veterinarians, Dr. Alexandra Wilson, DVM and Dr. Anthony Pilny, DVM, ABVP, giving their expert opinion about the trained parrots' condition. It is mainly evaluated based upon breast muscle, keel sharpness, breast shape, and checking for other fat deposits. A rounded or somewhat sharp keel bone is what we're looking for. Cleavage, where the breast meat/fat stick out past the keel bone, is a sure sign of obesity. Use this as a basic idea of what to consider, but then have your parrot evaluated by an avian vet to determine the optimal weight and condition for your bird.

I also opted to have some blood work done on one of the parrot's to check for any abnormalities or deficiencies. Since they are on similar diets, I decided one would be enough unless there were issues. Truman took one for the team and gave blood like a champ.

The blood chemistry turned out perfectly healthy and neither vet thought either bird was remotely underweight. In fact they both said they are at a good healthy weight and could safely be even lower. I brought them into the clinic at about the lowest typical weight I've been keeping them at lately. The training motivation at this weight is great, but I'm not doing it for that reason. I target the optimal healthy weight based on body condition and then take the training motivation byproduct that I get with it (which in fact is very high). Surprisingly the optimal healthy weight is much lower than the weight I would keep the birds at strictly for the sake of "starving them to make them do tricks." At the last vet wellness exam, the vet warned me that Kili was getting too heavy. The reason that happened was because I stopped weighing her and fed her as much as possible as long as she performed well. Well, I've since learned that this is not healthy and that I must manage the weight for health rather than just for training.

In conclusion, Kili & Truman are healthy parrots. Their weight is kept low with love for the sake of keeping them healthy and closer to what would be natural. Just because "nature" may be brutal, doesn't mean household life has to be. They get to live relatively sheltered lives, enjoy their health, and never have to starve. Their weight may be kept lower than if they were given unlimited food, but this is much healthier for them. Their condition and behavior is better as a result. Of the 3 avian veterinarians and many other experts, no one has ever told me that the birds are underweight, unhealthy, starved, malnourished, or in any way deprived. In fact they are considered healthy in all regards.

I could fill an entire book about this topic of food management, but there isn't sufficient interest yet. People don't realize just important it is. But food management isn't relevant just to professional trainers nor is it too difficult for responsible parrot owners to implement at home. Just like the attitude about seeds has changed to pellets, clipping is starting to change to flight, I hope to convince people the importance of managing how much food their parrots consume.

This article isn't meant to teach you how to food or weight manage. It is merely to try to convince you that food management is the way to go for the health of your parrot. I hope this article will convince you to begin learning about how you can nurture your parrot's health by ensuring it is fed the correct amount. Absolutely don't just reduce the amount your parrot eats without a significant understanding of how it is done properly. Keep in mind that some birds may already be at the right weight and that management should not be applied to baby birds, sick, or extremely elderly ones. The topic is quite extensive. I have written about it in great detail in my upcoming book, The Parrot Wizard's Guide to Well Behaved Parrots. It will be available by the beginning of June and it covers all aspects of accomplishing well behaved companion parrots.*

Comments

Posted on May 8, 2013 02:55PM

i am excited to see pictures of your baby as it matures.
here is my question...i live in Mexico and it is impossible to find pellets
or any managed diet feed for my parrots.
i like to make my own food for them..do you have any suggestions as to
what to be sure to include in their homemade blends?

Posted on May 9, 2013 01:23AM

Weight management is not a necessity for companion parrots. It is complex, time consuming, and terribly dangerous when implemented improperly. Free feeding may be the status quo and as long as the diet is low in fat and nutrient dense no vet is going to say it's an unhealthy diet. What a silly claim Micheal!
No real expert in the animal behavior modification field actually reccomends weight management for companion parrots OR ANY companion pet. Not Dr. Susan Friedman, Barbra Heidenrich, Steve Martin, Sid Price, Chris Biro, Bob Bailey, Karen Pryor, Emily Larlham, Rebecca O'Connor, I mean just name someone in the field and they will all shout out with a resounding "No" if asked to recommend weight management.
Weight management was designed for birds of prey to increase motivation to work and hunt for falconers. Its very definition means to get a bird to perform, Micheal. Whatever strange definition you have slapped onto "weight management" is far from the truth of what it really is.
By stating how "unnatural" it is to free feed a bird you succumb to the Appeal to Nature fallacy. You just assumed that because it doesn't happen in nature it must be "bad"! While it is true wild parrots do not spend all day eating, I hardly find it true that free fed birds eat all day. Which IS what you are indirectly saying. If this was true parrots would be stuffing themselves like goldfish an die from eating too much! [/b:2bqz4z67]
And for your concerns about bugs and rodents, well, I do hope that any responsible companion parrot owner does not have an insane infestation of rats and roaches in their home! Free feeding does not mean to have a food bowl in the cage when birds don't eat (at night), I hardly expect anyone would argue that this important for the bird. What an inane idea.
Again, you haven fallen for the appeal to nature fallacy and are assuming that because parrots eat in the morning and evening it is the best for them. What data do you have that actually concludes this? The research on parrots health and longevity related to WHEN they are fed a diet, is nonexistent. There are no conclusions to be drawn about your claim that free feeding is bad for a bird.
Have you taken a basic ecology class micheal? I'm assuming you have not and rather chose to major in computers or business because of this scrupulously written sentence:
"Simply put, there's not enough food for everyone."
Really? Is this so much more of a population pressure than age, stress and disease? Fully grown adult animals are not dropping dead in a healthy ecosystem because of "lack of food". This only happens (as you should have learned in ecology class) after an exponential population boom when the critical load to support a population has been reached. This is when dying due to lack of food becomes a problem.
When you say compare a bird to car on its last gallon of gas it worries me. It worries me in that you think it is acceptable to constantly have your car working on with that last gallon of gas in the tank. If you treat a car like this you shorten its life, and I suspect the same if this is how you treat a bird. We know this is true because weight management is much more than managing straight weight of the bird gram for gram. It's about making sure the bird has fat to burn. If the bird does not have fat its body will start to eat away at its muscle tissue to use for energy. Never have you once even mentioned this disastrous consequence from implementing weight management improperly. I doubt you are an expert in it at all.[/b:2bqz4z67]
I would certainly like to know where you got the idea that "parrots go days without food (in the wild)" it sounds like you are talking more about raptors than parrots.
This article is hardly convincing to the seasoned animal trainer to weight manage a bird. Managing what a bird eats however is far more important than micro-managing what the bird weighs. Birds should weigh differently over the seasons and their weight should be allowed to naturally fluctuate as such. To be restricted to the same weight all year should be considered cruelty.
Thanks for the article Micheal.

Posted on May 9, 2013 01:55AM

You, whoever you are, missed the point that parrots should be weight managed to the weight that is most healthy for them. Not starved, not underweight, not overweight. For most it is down. In some cases it's up or the same. There is nothing dangerous about weight being managed to the weight and body condition that is deemed most healthy by a veterinarian. That is just keeping the parrot healthy.
You also missed the major point that the reason less food has to go in (for the household parrot) is because less energy gets to go out through exercise. Clipped birds don't remotely come close to getting enough exercise but even flighted parrots in the confines of our homes and schedules get relatively little. Also the foods we tend to feed them are much more caloric than what they'd manage to find in the wild (corn and soy based pellets!? sunflower seeds?). The solution is either more exercise or less food, but since our abilities to grant sufficient exercise are limited, we have to resort to managing the food.
All of the avian veterinarians I have questioned complain about exceedingly more overweight parrots coming in with health problems than underweight. You only question the points that are of little significance. Fact is, owners need to be aware of their parrots weight and learn how to make adjustments in food quantity/quality to ensure it shifts to or stays at the healthy condition. This article is not about how but why.
Edit: But for people not paying full attention as they read, I went back and added this in bold to reiterate what I have already wrote:
Parrot's food intake should be managed such that they attain and maintain the optimal healthy weight as can be inferred from body condition by an Avian Veterinarian. I am not suggesting that the target weight should be determined by behavior, mathematics, guesswork, or chance.[/b:3jqb8m2e][/quote:3jqb8m2e]

Posted on May 9, 2013 07:12AM

Posted on May 9, 2013 05:57PM

Posted on May 10, 2013 03:09AM

Micheal there is a difference between monitoring a bird's weight to keep it healthy and weight management, please don't add additional confusion! Your definition of "weight management" in this article significantly differs from the actual meaning and use by professional falconers in which the idea was originally contrived for. This is a big misinterpretation on your part because this is what your article is discussing, is it not? You would be best replacing what you mislabel as "weight management" as "weight awareness".
I did not miss the point made in the post. You state calories in = calories out, no one can argue with that. But to go out and claim that "birds stuff themselves all day" as true? C'mon man, like I said if that were true pet birds would be popping like gorging goldfish. It just doesn't happen.
I agree that food management is a good idea[/b:1sfixyce], perfectly acceptable. This is what I believe you are trying to convey in this post. Birds CAN have scheduled meals in the day just like people. Zookeepers do it and their birds are healthy. And as an added bonus it can be much easier to train birds around their mealtimes as well. This is something every bird owner can do and is much more readily accepted by professionals in the field.
All of the avian veterinarians I have questioned complain about exceedingly more overweight parrots coming in with health problems than underweight.[/quote:1sfixyce]
And don't all avian vets! But calories in calories out right? Most avian veterinarians will not blame free feeding for this pandemic (and you seem so to keen to put down free feeding). It's seed-based diets causing the problem, end of story. Like I said, if a bird is free fed pellets and greens no vet is going to complain because the bird will not be over weight! What is it with you being against free feeding?
You only question the points that are of little significance.[/quote:1sfixyce]
Really? Because it seems all the little insignificant things add up Micheal. You use them to support your view but you will not defend them. Can you not?
Do these really seem like insignificant issues?:
Bird's do not stuff themselves full all day. If they do it is not considered normal!
Free feeding does not mean bugs and rats will infest one's home.
Using the Appeal to Nature fallacy over and over again is not small, but is what your entire argument is supported by.
Animals in a healthy ecosystem (especially parrots) don't drop dead over lack of food.
Bird's naturally fluctuate in weight over the season's and should be allowed to do so. To not allow a bird to do this is considered unhealthy.[/list:u:1sfixyce]
These "little" inconsistencies found in your post are topics that graduate students can write their major thesis about. These little things add up and makes a reader think that your blog is untrustworthy and not based on actual facts. This is not building trust with your audience Micheal, but breaking it.
Fact is, owners need to be aware of their parrots weight and learn how to make adjustments in food quantity/quality to ensure it shifts to or stays at the healthy condition. This article is not about how but why.[/quote:1sfixyce]
Yes! And you make it out to be more complex than it really is! Too much time on your hands? "Weight awareness" is all an owner needs. But then if it was that simple you wouldn't have something to sell this May.
What did your vet say in your video? "It's probably what we typically see, the majority of the birds are in the average body condition." Oh, did he just say weight management isn't needed to attain a healthy weight? I wonder what all those other bird owners are doing right...

Posted on May 10, 2013 04:21AM

I did not suggest "weight awareness." Merely being aware of it doesn't regulate it. When I say weight management, I mean that the "Parrot's food intake should be managed such that they attain and maintain the optimal healthy weight." Weight management is the active process of tracking, manipulating (through food availability), and maintaining a target weight. Where I differ from "experts" and those kind "zoo trainers" is that I do not recommend deprivation, starvation, desperation, or in fact any basing target weight on performance. I do not recommend evaluating behavior, motivation, performance, or behavior goals to determine or play a role in choosing a "target weight," "flying weight," or "training weight." I will get to maximizing motivation in the next article without straying from "healthy weight." Coincidentally, healthy parrots tend to be motivated parrots.
I didn't address your points because I said they are of little significance to the main point which is that captive parrots get little exercise, a lot of food, a lot of calories, reproductive triggers, and that since we have less control over those, we need to look to managing weight.
Freefeed doesn't necessarily mean there have to be pests but not leaving food out all day long is less likely to attract them. We don't leave food out elsewhere for a reason. I don't see a good reason for leaving it out for parrots (or pests) all day long.
Birds presented with food non-stop pick at it more from boredom. They will eat more when food is more available. If it is always available, they will put on more fat and maintain a higher weight. I've seen this in my birds, other people's birds, discussed it with vets, and it is common sense.
My appeal to nature is to demonstrate that parrots in the wild are not in fact on freefeed and to consider how their bodies are best evolved to operate. Since the human environment is quite different, we cannot make everything natural. Sometimes we have to apply unnatural means to achieve natural results. There are plenty of things that kill parrots in the wild and I'm not suggesting we accept them happening at home as natural. However, considering the natural elements helps us understand the dissonance of our home environments and gives us direction. Evolution has caused species to already reach equilibrium with environment pertaining to consumption vs work. At home that balance is entirely disrupted. The only way to regulate it is by encouraging as much exercise as we can and then making up the balance by reducing food consumption.
I base my food argument on my study of raptors and song birds. I don't know the mortality rates of parrots in the wild specifically but assume they are similar to other birds. Fact is most juvenile birds die of starvation and predation. Population takes its biggest hit on the young and old ends of the spectrum. "The evolutionary ecology perspective also defined the effect of adult mortality, first, on population density and, then, on reproduction rates through density-dependent effects on food availability. Seasonality of food is the key to these relationships. Birds of seasonal arid habitats in both Africa and Ecuador have larger clutches than do those in habitats that are humid year round at the same latitude. More generally, clutch sizes of birds relate directly to seasonal increases in food production rather than to absolute level of food production. This relationship exists because adult mortality in the cold or dry season of lowest food availability determines population density and baseline levels of food consumption in a habitat." (Ornithology Third Edition, Frank B. Gill p527)
Seasonal weight fluctuations are determined by environmental factors and food availability. If the parrot's weight is managed to stay fairly consistent, then reproductive activity will be suppressed. Reproductive activity is undesirable because it cannot succeed (for an unmated pet) but can create health and behavioral problems. Meanwhile molting and other demanding periods are automatically adjusted for by proactively "managing" weight rather than just observing it. When temperature decreases and birds metabolize more energy or they begin to molt, they will require a greater food consumption. Weight may momentarily begin to decrease and the food manager can quickly respond with a change in serving size to return to the target healthy weight. If regular training is performed, changes in motivation can also signal these needs. If parrots are regularly trained, they can earn additional fatty foods as treats. They have the ability to cope with metabolic changes accordingly. The actual weight does not need to change though as it is a closer reflection of body condition. Also, I have noticed that realistically these changes are minor compared to the change required to attain target healthy weight.
So these aren't little "inconsistencies". They're just less pivotal points that did not merit further explanation. But since you are so focused on them, there you are. I would rather direct attention to the fact that weight and body condition should be evaluated, and then adjusted through weight management to a targeted healthy weight. When that weight has been achieved, it should be evaluated again and further adjustments or equilibrium should be achieved.
Lastly your "experts" aren't relevant. Their papers about weight management almost exclusively pertain to outdoor freeflight parrots and zoo performing parrots. I am writing for the common parrot owner who's parrot does not remotely get the same amount of flight or exercise even if it spends all day out of the cage. I'm giving them the benefit of the doubt that their parrots are flighted but in reality most are clipped (and particularly overweight).
Through training (and with the help of taking some of the unnecessary weight off), greater amounts of flight exercise can be encouraged at home. But only to a certain extent. Since every individual parrot is different and every parrot's exercise regime is different, the only way to universally help everyone get their parrot to a healthy weight is to encourage maximum flight exercise and management of weight to a healthy body condition. Since that body condition is subjective and complicated, it is beyond the scope of this single article or discussion to present the way of achieving it.